Homeostasis, Balance, Stability


The fixity of the milieu supposes a perfection of the organism such that the external variations are at each instant compensated for and equilibrated…. All of the vital mechanisms, however varied they may be, have always one goal, to maintain the uniformity of the conditions of life in the internal environment…. The stability of the internal environment is the condition for the free and independent life.

Claude Bernard

The central principle of the General Theory in the construct of ‘Psychological Homeostasis’. Sixty-one years after Bernard (1865) wrote about the ‘internal milieu’, Walter B. Cannon (1926) coined the term ‘homeostasis’. Then, 16 years later, psychobiologist Curt Richter (1942) expanded homeostasis to include behavioural or ‘ total organism regulators’ in the context of feeding. From this viewpoint, ‘external’ behaviours that are responses to environmental stimuli lie on a continuum with ‘internal’ physiological events. For Richter, behaviour includes all aspects of feeding necessary to maintain the internal environment. Bernard, Cannon and Richter all focused on a purely physiological form of homeostasis, ‘H[Φ]’. I wish to convince the reader that the hypothesis of the ‘external milieu’, the proximal world of socio-physical action, is equally important.

The General Theory extends homeostasis to all forms of behaviour. Psychological homeostasis can be explained in two stages, starting with the classic version of homeostasis in Physiology, H[Φ], followed by the operating features of its psychological sister, H[Ψ]. The essential features are illustrated in Figure 2.1.

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Figure 2.1 Upper panel: A representation of Physiological (Type I) Homeostasis (H[Φ]). Adapted from Modell et al. (2015). Lower panel: A representation of Psychological (Type II) Homeostasis (H[Ψ]).

To be counted as homeostasis, H[Φ], a system is required to have five features:
1. It must contain a sensor that measures the value of the regulated variable.
2. It must contain a mechanism for establishing the “normal range” of values for the regulated variable. In the model shown in Figure 2.1, this mechanism is represented by the “Set point Y”.
3. It must contain an “error detector” that compares the signal being transmitted by the sensor (representing the actual value of the regulated variable) with the set range. The result of this comparison is an error signal that is interpreted by the controller.
4. The controller interprets the error signal and determines the value of the outputs of the effectors.
5. The effectors are those elements that determine the value of the regulated variable. The effectors may not be the same for upward and downward changes in the regulated variable.

Identical principles apply to Psychological (Type II) Homeostasis (H[Ψ] with two notable differences (Figure 2.1, lower panel). In Psychological Homeostasis, there are two sets of effectors, inward and outward, and the conceptual boundary between the internal and external environments lies between the controller and the outward effectors of the somatic nervous system, i.e. the muscles that control speech and action. Furthermore, Psychological Homeostasis operates with intention, purpose, and desire.

The individual organism extends its ability to thrive in nature with Type II homeostasis. Self-extension by niche construction creates zones of safety, one of the primary goals of Type II homeostasis. Niche construction amplifies the organism’s ability to occupy and control the environment proximally and distally. The use of tools for hunting, weapons for aggression, fire for cooking, domestication of animals, the use of language, money, goods for trade and commodification, agriculture, science, technology, engineering, medicine, culture, music literature and social media are all methods of expanding and projecting niches of safety, well-being and control. Individual ownership of assets such as land, buildings, companies, stocks and shares reflect a universal need to extend occupation, power and control but these possessions do not necessarily increase the subjective well-being of the owner [AP 007].

Initiated by the brain and other organs, homeostasis of either type can often act in anticipatory or predictive mode. One principal function of any conscious system is prediction of rewards and dangers. A simple example is the pre-prandial secretion of insulin, ghrelin and other hormones that enable the consumption of a larger nutrient load with minimal postprandial homeostatic consequences. When a meal containing carbohydrates is to be consumed, a variety of hormones is secreted by the gut that elicit the secretion of insulin from the pancreas before the blood sugar level has actually started to rise. The blood sugar level starts lowering in anticipation of the influx of glucose from the gut into the blood. This has the effect of blunting the blood glucose concentration spike that would otherwise occur. Daily variations in dietary potassium intake are compensated by anticipative adjustments of renal potassium excretion capacity. That urinary potassium excretion is rhythmic and largely independent on feeding and activity patterns indicates that this homeostatic mechanism behaves predictively.

Similar principles operate in Type II homeostasis acting together with the brain as a “prediction machine”. When we anticipate a pleasant event such as a birthday party, there is a preparatory ‘glow’ which can change one’s mood in a positive direction, or thinking about an impending visit to the dentist may be likely to produce feelings of anxiety, or the receipt of a prescription of medicines from one’s physician may lead to improvements in symptoms, even before the medicines are taken.

At societal level, anticipation enables rational mitigation, e.g. anticipation of demographic changes influences policy, threat from hostile countries influences expenditure on defence, and the threat of a new epidemic influences programmes of prevention. [AP 008].

Homeostasis involves several interacting processes in a causal network. A homeostatic adjustment in one process necessitates a compensatory adjustment in one or more of the other interacting processes. To illustrate this situation, consider what happens in phosphate homeostasis (Figure 2.3). Many REF-behaviours that we shall refer to are isomorphic with the 4-process structure in Figure 2.2. However, in nature there is no restriction on the number of interconnected processes and any process can belong to multiple homeostatic networks.

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Figure 2.2 Phosphate homeostasis. A decrease in the serum phosphorus level causes a decrease in FGF23 and parathyroid hormone (PTH) levels. Increase in serum phosphorus leads to opposite changes. Calcitriol increases serum phosphorus and FGF23, while it decreases PTH. Increase in FGF23 leads to decrease in PTH and calcitriol levels. PTH increases calcitriol and FGF23 levels. Reproduced from Jagtap et al. (2012) with permission.

Homeostasis never rests. It is continuous, comprehensive and thorough. With each round of the REF, all of the major processes in a network are reset to maintain stability of the whole system. The REF process goes through a continuous series of ‘reset’ cycles each of which stabilizes the system until the next occasion one of the processes falls outside its set range and another reset is required.
Processes in Type II homeostasis may vary along quantitative axes or they can have discrete categorical values. For example, values, beliefs, preferences and goals can have discrete values, as does the state of sleep or waking.

Any change in a categorical process involves change throughout the network to which is belongs. [AP 009].

Such changes may be rapid, in the millisecond range, e.g. a changed preference from chocolate chip cookie flavoured ice cream to Madagascar vanilla that may occurs an instant after arriving at the ice-cream kiosk. At the other end of the spectrum of importance, in buying a new apartment, the final choice might also occur in the instant the preferred option is first sighted. Or the decision could take months or years even though it is of precious little consequence, e.g. deciding that one is a republican rather than a monarchist, or it may never occur because we simply do not care one way or the other. These considerations lead to a surprising proposition that:

The speed of a decision is independent of its subjective utility [AP 010].

One objective of A General Theory of Behaviour is to explain the relevance of the REF system to Psychology. We know already that the regulation of action is guided by three fundamental systems: (i) the brain and central nervous system (CNS), (ii) the endocrine system (ES) and (iii) the immune system (IS). It is proposed that, as a ‘meta-system’ of homeostatic control, these systems collectively govern both physiology and behaviour using two types of homeostasis, H[Φ] and H[Ψ], respectively. We can understand how this might be possible in light of a recently discovered ‘central homeostatic network’.

An extract from: A General Theory of Behaviour.

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